Multioffice telephone system



May 16, 1933. J. WICKS ET AL MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet l vsm unh I l I I l I I I I I I ll 5a J A 1 m s u Wm P .1 U a wn. n mm \mm Wm N .%M 0 H mxzmm 226 r W Y I El WM) N i W 3 W 3 $9 w E w 3 m4 a 5 ck Kl. H A E \w v m g (Q m V in 2 EE :3

12 Sheets-Sheet 2 J. WICKS ET AL MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 May 16, 1933.

-Im.rEn Dr's-'- Jnhn wicks Rog F. Gould J. wlcKs ET AL 1,909,082

MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 3 May 16, 1933.

May 16, 1933. J. WICKS ET AL 1,909,032

MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 4 nhn Wicks May 16, 1933. J. WICKS ET AL 1,909,082

MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Shqets-Sheet 5 Fi.4 uar E 407 T WO'STEP TWO-STEP -I&mm-s-- John wicks May 16, 1933. J. WICKS El AL MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 6 MNIQ ImrEn cars John E'Jwks J. WICKS ET AL MULTIOFFICE TELEPHONE SYSTEM May 16, 1933.

Original Filed March 3, 1930 12 Sneets-Sheet 7 JD An Hicks RUFF Guu'lcl May 16, 1933. J. w s AL 1,909,082

MULTIOF'FICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 8 John ln wk s Ru FEuuld May 16, 1933. .1. WICKS ET AL MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 9 y 1933- J. wlcKs El AL MULTIOFFICE TELEPHONE SYSTEM Original Filed March 3, 1930 12 Sheets-Sheet 10 iii) W mm ITLUE'I1DI"E" John wicks HEN-.11 F Gould May 16, 1933. J. WICKS ET AL 1,909,032

MULTIOFFICE TELEPHONE SYSTEM Original Filed March 5, 1950 12 Sheets-Sheet 12 LOCAL 805) John wicks Patented May 16, 1933 UNITED STATES PATENT OFFICE .Iorm WICKS, or oAxrAax, AND my I. GOULD, or CHICAGO, Immors, AssIGNoas, BY MESNE ASSIGNMENTS, TO ASSOCIATED ELECTRIC LABORATORIES, INC, or CHICAGO, ILLINOIS, A CORPORATION or DELAWARE MULTIOFFICE TELEPHONE SYSTEM Application flied March 3,1930, Serial No. 432,688. Renewed June 27, 1932. v

it This invention relates in general to multi ("lice telephone systems, particularly to multio'ffice automatic telephone systems in which the switching apparatus employed in one or more offices is operated according to a method of control different from that of the switching apparatus employed in other offices of the system. The object of the invention, broadly stated, is the provision of new and improved circuits and apparatus for supplying local and toll service as well as various auxiliary services in systemsof the above type.

The invention is particularly adapted for systems of the so-called.inverted type in which talking and operating current is fed from the first switch of the train instead of from the last switch. A system of this type employing the loop method of control is shown in the co-pending application of J. Wicks, Serial No. 395,882, filed September 28, 1929'. A system of the type employing the single conductor method of control, that is, in which current impulses are transmitted ahead over only one conductor of the local trunks is described in Die Fernsprechanlagen mit Wahler-Betrieb by Lubberger, second edition, 1924,- and representative circuits are shown in the supplement, pages 4448.

Both of the'above systems arewell known and are used commercially. In certain instances ithas been found advisable to employ apparatus of both systems in a single multioffice network, in which case it is necessary to provide special interconnecting facilities.

The problem of providing such facilities is complicated by the necessity of supplying various auxiliary services such as timeand zone metering and preferred toll and trunk services. Further complications arise from the fact that the switches of the two systems are normally adjusted to operate on'a slightly different pulse ratio or length. of impulse. While the difierence is not great, it narrows the operating range of the switches and may readily become a source of trouble when the directive impulses are transmitted over relatively long trunk lines, or are repeated through several tandem offices. This operatingcha'racteristic must betaken into cona preliminary warning tone after which the local connection is released and the trunk" connection established. A somewhat similar servicehas been supplied in the past in connection with toll operation, that is, the toll operator by ringing or by dialling an additional digit has been able to cut-in on a local connection and establish the preferred call. In so far as applicant is aware, this type of service has not previously been extended to subscriber control trunk calls or handled on an automatic basis.

Another feature of the invention is the arrangement for regenerating the directive impulses on calls between offices of different types in order to prevent faulty operation due to impulse distortionor differing pulse ratio.

A further feature is the arrangement for metering trunk and'toll calls, including improved timing' switches and arrangements for automatically cutting an auxiliary timing apparatus into service in case of failure of the regular apparatus.

- A still further feature is the arrangement for switching calls to an operators position and releasing the exchange switching apparatus; v

The foregoing features together with others not specificallymentioned at this time will be further discussed in connection with the detailed description of the operation of the various circuits.

The accompanying drawings comprising Figs. 1 to 11, inclusive, show by means of the usual circuit diagrams a sufficient amount of equipment in a system embodyinglthe invention to permit the invention to be readily described and understood. Only such switchoperation description. This apparatus is assumed to be located in two oliices of a multi-ofiice network, the oflices employing, respectively, the two types of apparatus previously referred to. It is to be understood, however, that this particular embodiment of the invention is shown only for convenience of description.

Referring now to the drawings. In Fig. 1 is shown an automatic substation T whose associated line terminates in a lineswitch LS and is accessible in the banks of connectors, such as the connector C. Lineswitch LS is one of a group of similar switches terminating subscribers lines and having access to a group of trunks extending to selectors, such as selector S. The lineswitch which is shown only in skeleton form may be of any suitable type, or, if used, line finders may be used. Selector S is of the type adapted to feed battery to both calling and called subscribers and to repeat impulses to the other switches of the train. This selector is arranged to absorb one or more digits in order that a uniform numbering scheme may be used throughout the system, but this particular feature is not concerned with the invention. Selector S and other corresponding selectors have access to local trunks and outgoing trunks. The local trunks terminate inintermediate selectors, such as the selector S1, and the outgoing trunks terminate in repeaters, such as the repeater B, (Fig. 3) which will be described in later paragraphs. Selector S1 may be similar to the intermediate selector disclosed in lVicks Patent No. 1,778,204, granted Oct. 14, 1930, modified however by addition of a fourth wiper for purposes which will be discussed hereinafter. Selector S1 and corresponding selectors have access to combination toll and local connectors C which in turn have access to subscribers lines, such as the one extending to substation T1. Connector C is arranged to operate as a local connector when seized by a calling local subscriber and as a toll connector when seized in a toll call. This connector may be the same as the combination toll and local connector disclosed in the previously referred to Wicks application, Serial No. 395,882. Substation T1 will be similar in all respects to substation T, and will have an associated lineswitch corresponding to line switch LS.

Fig. 2 shows an incoming toll selector ITS associated with a two-way inter-office trunk. This trunk which terminates in one exchange in the repeater R is accessible to local selectors, such as S, for extending calls to the other exchange. Selector ITS is operated on incoming calls over the trunk and has access to subscribers in the exchange by way of intermediate selectors, such as selector S1, and connectors, such as connector C.

Fig. 3 shows a repeater R terminating one end. of the two-way trunk line TL extending to a distant ofiice. Associated with this repeater are the incoming selector ITS previously referred to, lineswitch LS1, and an individual timing switch IT. Lineswitch LS1 serves to connect up an idle regenerating repeater G (Fig. 4:), and timing switch IT controls the elapsed time metering as will be described hereinafter.

In Fig. at, parts 1 and 2, there is shown an impulse regenerating repeater or register sender switch. which is adapted to be associated temporarily with a repeater, such as repeater B. On outgoing calls over the trunl\ the dialled impulses are registered in this repeater which in turn retransmits correspending impulses of the proper type to operate the switches at the distant end of the trunk. The switch consists essentially of a relay distributor, a group of pulsing relays, a control switch CS, and a group of register switches RS1, RS2 and RS3.

In Fig. 5 is shown the individual timing switch IT associated with a repeater B. This timing switch together with other similar switches associated with other repeaters have access to a common bank multiple together with the master timer MT. CT is a cam timer associated wth master timer MT and its function is to supply pulses of the proper frequency to operate the master timer.

'Fig. 6 shows a pendulum timer PT and a timer transfer circuit TT. The pendulum timer is associated with and individual to the cam timer CT and controls the operation thereof. The master timer, cam timer, and pendulum timer are common to all individual timing switches of the exchange. Inasmuch as this common equipment has a very important function to perform, it is desirable to provide a duplicate set to be used in case of failure of one or more of the common switches. The transfer circuit TT is arranged to switch over and connect up the auxiliary timing set in case of such trouble. The auxiliary apparatus is similar in all respects to that shown with the exception of the mechanical starting device associated with the pendulum timer of the auxiliary apparatus.

Fig. 7, parts 1 and 2, show a repeater R1 associated with the other end of the trunk line TL. Two branches extend from the repeater, one terminating in a selector, such as the selector S2, and the other terminating at a manual position or toll board, Fig. 8. The discriminating switch DS associated with the repeater responds to certain of the digits dialled over the trunk and controls the branch over which the call is to be extended.

In Fig. 8 there are shown various circuits located at the manual position or toll board,

- oflice of the same or another system.

including the trunk apparatus TA termi nating the trunk incoming fromrepeater R1, thetrunk relays TB- in which a selector level trunk terminates and the toll line jack J3 terminating a trunk line extending to anoti iler e cord circuit or link L may be of any well known type suitable for interconnecting the various trunks and is shown only in skeleton form. The dialling cord DC is adapted to be associated with thetrunk extending to repeater R1 for COIltIOlliIlg the switches at the exchange terminating the other end of the trunk line TL. It is to be understood that in practice there will be a plurality of the various trunk lines as Well as link circuits at the toll board. There will ordinarily be one dialling cord common to the position.

In Fig. 9, T2 represents an ordinary automatic substation whose associated line terminates in lineswitch LS2 which may be similar to lineswitchLS previously described or may be any well known type of lineswitch or line finder. The lineswitch has access to local first selector S5 which is of the general type described in the previously referred to Lubberger book. The first selectors have access to various groups of intermediate selectors represented respectively by the selectors S3 and S4. Selectors S 1 have access to local connectors (not shown) and to trunks extending to the toll board, such as the trunk terminating in relay group TR. Selectors S3 and S4 may be similar in all respects to, selector S2. Selector S2 incidentally is directly associat ed with repeater R1 and has access to the intermediate selectors in common with selector S5. The intermediate selectors have access to the connectors as-previously mentioned, the group represented by selector S3 having access to combination connectors, such as connector C1 10).. y

In Fig. 10 is shown a combination toll and local connector G1 which has access to regular subscribers lines to the exchange of which one line terminating in substation T3 is shown.

Fig. 11 is alayout diagram showing how the various sheets of drawings should be arranged inorder to be best understood.

From the foregoing description it will be obvious that the apparatus shown in Figs. 1 to 6, inclusive, is located in one exchange while that shown in Figs. 7 to 10', inclusive,

is located in another exchange. It may be further noted that the apparatus located in thefirst' exchange is operated according to the loop method of control while that located in the second exchange is operated according to the single conductor method of control. These oflices will be identified in later paragraphs by referring to them, respectively, as the first and second exchanges or ofiices.

Havingdescribed the various units of apparatus and their interrelation, the operations involved in setting up various connections in the system will'now be described briefly. e

Local calls in the first exchange do not involve any of the features of the invention. A call from substation T' to substation T1 is extended by way of lineswitch LS, local first selector S, intermediate selector S1, and connector G in the well known manner. Local calls of this kind involving similar switches are described in detail in the previously referred to Wicks application, Serial No. $195,882 and will not be described in detail ere.

The subscriber at substation T in calling a'subscriber at substation T3 in the second exchange completes the call in the usual manner by dialling the number of the wanted .subscribers telephone. Lineswitch LS operates the usual way to extend the calling line to a local first selector S which is then dialled up to the level assigned to trunks extending to the second exchange, which in this case will be assumed to be the sixth level. The selector seizes an idle trunk which may be the one terminating in repeater R, and the connection is then extended over the trunk line TL to repeater R1 and through that repeater to a selector S2. Incoming selector ITS is disconnected from the trunk and lineswitch LSl operates to connect up an idle ing digits of the wanted subscrihers number,

these digits being recorded in the regeneratingrepeater which in turn retransmits corresponding impulses through repeaters R and R1 to operate selectors S2 and S3 and connector C1. In case the called line is idle connector C1 signals the wanted subscriber, and when that subscriber answers, returns a supervisory condition over the trunk whereby the individual timing switch IT operates to start the metering of the call under control of the Various common timing switches. The regenerating repeater is released as soon as the idle line is connected with or, in the case of an incompleted call, is released after a predetermined time. called line is busy in a local. connection, repeater R1 will operate to cause the connector switch C1 to cut-in on the busy line and momentarily apply a busy tone both to the trunk and to the wanted 'line. interval repeater R1 will then cause the connector to release the local connection and es tablish the trunk connection. In case the line is busy in a toll call a busy tone will be given to the calling subscriber but no further operations will take place.

Should the subscriber at substation T desire to call the toll operator, the procedure would be the same as in the previous call except that the firsttwo digits would so position the distributor switch DS in repeater Intheevent that the I After a short R1, that the local switch train including selectors S2 and S3 would be released and the call extended over the trunk TA to the operators position. The operator would then further extend the call by way of a link circuit, such L, and would further control the metering by ope-rating one of the metering keys. The particular liey operated determines whether the calling subscribers meter will be operated once for each unit of time or a plurality or times for each unit of time consumed by the call.

The subscriber in the second exchange, such as the subscriber at substation T2, on calling subscriber in the first exchange, will dial the two digit code assigned to the operator whereby the call will be extended over a trunk line, such as TR. The operator on determining the number of the wanted subscriber will establish a connection with an idle trunk, such as the trunk TA, by means of: link circuit L, and will then connect up t 1e dialling cord DC to the selected trunk and dial the wanted subscribers number. Selectors corresponding to incoming selector ITS and intermediate selector S1 and a connector, such C, will be positioned to extend the call to the wanted subscribers line. If the wanted line is idle the connection is completed in the usual way, however, if it is busy in a local 0111120131011 the operator is given a distinctive tone and may then interrupt the local connection and complete the trunk connection. The timing switch IT and regenerating repeater G do not function in this type of connection.

Toll calls are completed in exactly the same manner as the previously described trunk connectien from the second exchange to the first exchange.

In connection with the metering switches it may be pointed out that the switches shown are normally connected up to provide this service. In case the regular apparatus fails to function properly, the transfer circuits TT automatically disconnect the regular apparatus and connect up the auxiliary apparatus so that at no time will the exchange be without the necessary metering device.

Having briefly described the apparatus and the operations involved in setting up various conneutions a detailed description will now be entered, on.

A call from substation T in the first exchange to substation T2 in the second exchange will first be described. hen the subscriber in substation T lifts his receiver, the usual loop circuit is established and lineswitch LS rmerates in the well known manner to select an idle trunk, which, in this instance, will be assumed to be the trunk extending to selector S. Relay 101 will operate over a circuit from battery, lower winding of relay 102, loftand coil of relay 101. contacts 137, contacts 5 of the lineswitch bank, through the lineswitch, line conductor 1, through the loop of the calling substation, conductor 2, through the lineswitch, contacts 8 of the lineswitch bank, contacts 145, right-hand coil of relay 10], upper winding of relay 102 to ground. Relay 102, which is dillerentially wound, does not operate at this time. Relay 101 on operating closes a circuit from ground, contacts 127, winding of relay 108, both windings of relay 107 in series to battery, and in parallel with relay 107, through contacts 119 and 179, winding of vertical magnet 112 to battery. Relay 108 operates, but due to its resistance, relay 107 and magnet 112, do not operate at present. Relay 101 also closes a circuit from battery tl'irough the lower winding of relay 102, winding of relay 103, contacts 125, 138, and 173, upper winding of relay 106 to ground. Relays 103 and 106 operate over this circuit but relay 102 does not operate due to the resistance of the upper winding of relay 106. Relay 108 upon operating connects ground to the release trunk at contacts 163 to hold the lineswitch in operated position and for other purposes which will become apparent as the description progresses. Relay 108 also prepares the impulsing circuit at contacts 165. Relay 106 upon operating connects dial tone to the upper alking corrductor by way of oil-normal contacts 123 and contacts 1&8, prepares the circuit of relay 110 at contacts 150, and closes a holding circuit for its lower winding by way of contacts 152 and 133. The calling subscriber on hearing the dial tone is advised that a free switch has been seized and that dialling may commence.

It may be assumed, for the purpose of this description, that the number of the wanted substation is 65 132 and that the calling subscriber proceeds to dial this numher in the instant connection. The calling loop is therefore interrupted six times by the calling device at the substation in response to the dialling of the first digit and relay 101 responds accordingly. Each time relay 101 restores, relay 108 is short-circuited at contacts 128 and relay 107 and magnet 112 operate due to the increased current flow. Relay 107 is slow-to-deenergize due to its series connection with relay 108 and consequently, remains operated throughout the series of impulses. Magnet 112 operates for each impulse and raises the wipers step-bystep to the sixth level. WVith each impulse a holding circuit is completed for relay 103 extending from the winding of that relay, contacts 126, resistance 11, oil-normal contacts 124 closed on the first Vertical step of the wipers, contacts 130, 139, and 158, to ground. Relay 102 is prevented from operating at this time by the resistance 114; in the above circuit. l/Vhen relay 107 restores shortly after the last impulse of the series, a circuit is completed from ground at contacts 163, ofl-normal contacts 124, contacts 130, 139, 157, 177, and 118 through the winding of rotary magnet 111, to battery. The rotary magnet operates and steps the wipers in on the first set of contacts on the sixth level. In case the trunk terminating in these contacts is busy, wiper 182 will encounter a -ground with the result that magnet 111, which in the meantime has interrupted its own circuit at contacts 118 and deenergized, will again operate over the previously traced circuit and advance the wipers to the next set of contacts. Assume that the first idle trunk encountered is the trunk comprising conductors 43+45 terminating in repeater.

R (Fig.3). The following circuit is completed when this trunk is reached: ground,

contacts 164 and 150, upper winding-of relay 110, wiper 182,conductor 44, contacts,

238, conductor 368, winding of relay 301 to battery. Relays 110 and 301 operate over the above circuit. Relay 110 stops further rotation of the switch by opening contacts 177 and at contacts 176 closes a holding circuit for its lower winding in series with ma'g-' net 111. Magnet 111 does not operate at this time due to the high resistance of the winding of relay 110. The talking conductors areconnected through atcontacts 172 vertical magnet is disconnected.

Referring now toFig. 3, relay 301 upon operating closes a circuit from ground, contacts 319 and 327, lower winding of magnet381 of lineswitch LS1, contacts 382 to battery at the master switch MS, Magnet 381 operates and forces the plunger into the banks to close contacts 392395 and also completes a holding-circuit for .its two windings in series by opening contacts 382 and closing contacts 383. The closure of contacts392 marks'the trunk busy and causes the master switch to align the remaining plungers opposite another trunk. It has been assumed, for convenience, that the lineswitch is standing opposite the trunk comprising conductors 396-399 terminating in the re ngeneratingrepeater G. A circuit may now be traced from battery, lower windingv of relay102, winding of relay 103, contacts 125,138, and 172,wiper 181, conductor 43,-

conductor 367, contacts 315, conductor 386, contacts 395, conductor 399, through the windingof relay 401 to ground. Relay 103,

which was previously held energized over a local circuit inthe selector S,'is now held .ductor 384.

operated over the above-traced circuit, and in turn. maintains the holdingcircuit for relay 106. It may be mentioned at this point, that in local calls the circuit for relay 103 will extend over wiper 181 and through the impulsing relay of the local switch thence back over wiper 183, contacts, 180 and 144, winding of relay 104 to ground. A loop circuit has been dispensed with in the present instance for'purposes-which willbe clear when the further operations of the switches is considered.

Referring again to Fig. 3, relay 301 in operating further connects ground to conductor 377 at contacts 316 for purposes whichwill be described later, disconnects ground from conductor 369 at contacts 318and prepares a holdingcircuit'for relay 302 at contacts 317, and connects the dialling leg of the associated trunk'line, conductor 380, by way of contacts 322*and 329, conductor 385, contacts 394, conductor 398, contacts 438, upper winding of relay 409 to battery. Conductor 380 which is the dialling leg of the trunk line TL, extends to ground atthe distant office as will be subsequently explained and relay 409 consequently operates and closes a circuit from and operates only its contacts 324 at this time.

The lower or operating winding is 'nowv short- 'circuited by ground through contacts 317 and the relay consequently remains in its first position until ground 1s removed from con- Referring nowto Fig. 4, relay401operating, closes acircuit for relay 402 at contacts 418. Relay 402 operates, connects ground to test conductor 396 at contacts 420, closes a point in the automatic releasing circuit at contacts 421, vprepares the impulsing circuit of'contacts 422, and grounds the local holdiing conductor 461 at contacts 424. Relay 411 operates from ground on conductor 461 by way of contacts 451, and connects ground to holding conductor 464 at contacts 446.

' The calling subscriber-now dials the second digit-"of the called number, that is, the digit 5, and relay l0lresponds as in the previous instance. The circuit of relay 401, previously traced, is intermittently opened at contacts 125, and relay 401 deenergizes and reener- 'gizes in step with relay 101. The previously noted holding circuit for relay 103 is again" closed at contacts 126 during the transmission of this series :of impulses. Each time .relay 401 retracts its armatures, a circuit is closed from ground, contacts 419 and 422, winding of relay 403, conductor 460, contacts 426 and .436, winding of stepping magnet 409 of register switch RS1 to battery. 'Magnet 409 operates in response to these impulses and steps wiper 415' around to the fifth contact, that is, contact 47 8, of its bank. .Relay 403 operates in response to the first impulse, and due to its slow-releasing character, remains operated throughout the series of impulses. A circuit is thereby closed from ground at contacts 424, contacts 428, conductor 462, contacts 433 and 424, lower winding of relay 401 to battery. Relay 401, which is a two-step relay, operates in its first step over the above circuit and closes only its contacts 422, thereby preparing its operating circuit. Shortly after the last impulse of the series, relay 403 restores and removes ground from conductor 462. Relay 401' now operates in its second step from ground on conductor 461, contacts 428 and 422, and the two windings of the relay in series. The impulsing circuit, including conductor 460, is transferred by way of contacts 425' and 435 to magnet 410 of register switch RS2. Conductor 462 is disconnected from relay 401 at contacts 424 and connected instead to relay 402 by way of contacts 423 and 431. Off-normal contacts 418, which close when wiper 415 is moved from normal position, complete an auxiliary holding circuit for relay'401 to keep that relay operated as long as the register switch RS1 is off-normal.

Relay 401' upon operating in its second step also completes a circuit from ground through the winding of release magnet 412 of register switch RS1, contacts 427 conductor 463, wiper 416 of control switch CS in' first position, winding of relay 413 to battery. Relay 413 operates over this circuit but the magnet does not. Relay 413 closes a circuit from ground, contacts 453, 455, and 441, winding of relay 406 to battery. Relay 406 operates, completes a temporary locking circuit for itself at contacts 436 and closes a circuit for relay 407 at contacts 435. Relay 407 operates and closes a circuit for relay 408 at contacts 440. Relay 407 also disconnects relay 409 from conductor 398 thus transmitting an impulse over the dial leg of the trunk. A temporary holding circuit is closed for relay 409 at each impulse, this circuit extending over contacts 439 and resistance 458 to ground at contacts 424. Re-

lay 409, therefore, remains operated and maintains the ground on conductor 397 so that relay 302 is prevented from operating in its second step at this time. Relay 408 now operates and opens the circuit of relay 406 which deenergizes and in turn opens the circuit of relay 407. Relay 407 restores, reconnects battery to relay 409 to conductor 398 and opens the circuit of relay 408 which likewise restores. This cycle of operation is repeated for each impulse. The length of the impulses and the intervals between them can be very accurately regulated by varying the adjustment of the relays 406- 408. Incidentally relay 401 may be adjusted to operate over a wide range so that it will respond properly to impulses which may be somewhat distorted by being repeated through several tandem exchanges, or by variation in the calling devices at the subscribers substation. The impulsing relays, however, will retransmit the impulses over the trunk entirely free from distortion and at the proper rate of speed to give the best results with the equipment used. These relays further control the impulse ratio, that is the ratio between the open circuit and closed circuit periods of each impulse, and by proper adjustment will transmit the particular type of impulse for which the switching apparatus is adjusted.

Each time relay 406 operates, a circuit is closed from ground at contacts 436 or 453, contacts437 to conductor 465. During the transmission of the first impulses, this ground extending through contacts 469, 462, 455, and 448, through the lower winding of relay 404 to battery, causes relay 404 to operate in its first step and prepare a circuit for both of its windings in series at contacts 446'. Relay 406 restores at the end of the impulse and disconnects ground from conductor 465 by opening contacts 437, thereby removing the short circuit from the upper-winding of relay 404 and that relay operates in its second step. The operating circuit including conductor 465 is thereby transferred to relay 405 by way of contacts 447. Relay 404 remains operated over contacts 446 and and 451, and conductor 464 to ground at contacts 446. On the transmission of the sec 0nd impulse, relay 405 operates in the same manner as relay 404 had previously operated, and the impulsing conductor is transferred to relay 406' at contacts 454. Relay 405 opens the circuit of relay 404 at contacts 451 and that relay restores. Relay 406' responds to the third impulse, relay 407 responds to the fourth impulse, and relay 408 responds to the fifth impulse, which, in this case, is assumed to correspond to the digit registered on switch RS1. A circuit is now closed from battery, winding of relay 412, contacts 450, conductor 466, contacts 477', contact478 of the bank register switch RS1, wiper 415, wiper 417 of control switch CS in first position, contacts 455 and 453, to ground. Relay 412 operates over this circuit and locks to conductor 464 at contacts 449, opens the circuit of relay 411 at contacts 451, disconnects ground from the previouslytraced operating circuit at contacts 453, and shunts relay 413 with battery through resistance 467 at contacts 454. Relay 412 prevents the further operation of the impulse relays by opening contacts 453. The current flow through resistance 467, which is now connected in parallel with relay 413, is sufiicient to cause the operation of release magnet 412', which restores wiper 415 to normal position. Ofi-normal contacts 418 are now opened, and in the event that the second digit .of a series of impulses in thesame manner as described for the registration of thefirst digit. The impulsing lead 460 is then transferred to magnet 411'. of register switch RS3 by way of contacts 425 and 434 in case both relays 401 and 402 are operated and over contacts 426 and 436. after relay 401 restores. The third digit is registered on switch RS8 and relay 403' operates in its second step shortly after the last impulse of the series and transfers impulse conductor 460 back to magnet 409 of register switch RS1. The above cycle of operation is repeated for subsequent digits, the fourth, fifth, and sixth (if there are that many) being registered respectively on register switches RS1, RS2, and RS3. The retransmission of impulses is very rapid and the first register switch is cleared before the calling subscriber can possibly dial the fourth digit.-

Referring back to the retransmission of the first digit, relay 412 upon operating opened the circuit of relay 411. Relay 411 is slow-to-release and a short interval after its circuit opened the relay restores, opens the circuit of relay 412, and closes a point in the circuit of stepping magnet 456 of control switch CS at contacts 447. Relay 412' is also slow-to-release and maintains its armatures operated a short intervalafter its circuit is opened. Duringthis interval magnet 456 is operated from ground by way of contacts 452 and 457, and wipers 416 and 417 are advanced to second position.

The retransmission of the second digit is similar to that of the first digit, the starting circuit, however, extending through contacts 438. and wiper 416 of control switch CS in second position. The stopping circuit for this digit includes wiper 416 of register switch RS2, on which the second digit was registered, and wiper 417 of control switch CSin second position.

The manner in which subsequent digits are retransmitted will be obvious from the foregoing description. The first, fourth, and seventh contacts; second, fifth, and eighth contacts; and third, sixth, and ninth contacts of the banks of the control switch OS are multiplied so that the register switches RS1, RS2, and RS3,'will function, respectively, for each fourth digit of a called number.

The release of relay 411, as previously described, removes ground from conductor 464 at contacts 446 and any of relays 404'- 408, which were previously locked up, are released and the apparatus is in condition to retransmit the second impulse.

The operation of the counting relays was described for the retransmission of a digit comprising. five impulses. For digits comprising a greater number of impulses, such as ten impulses, for example, relays 404408' will operate responsive to the transmission of the first five impulses in the same manner as previously described. Relay 408? will remain locked up permanently, and relays 404'407' will release. Relay 404 will lock permanently for the sixth impulse, relays 405' and 406 will lock temporarily for the seventh and eighth impulses, respectively, relay 407 will lock permanently forthe ninth impulse, and relay 405 .will lock permanently for the tenth impulse. I Relay 406' is available for an eleventh impulse if such is required. The operation of the counting relays in the above manner connects ground to successive contacts of the register switch banks,'the wipers of which are positioned according to the digit to be retransmitted. The release relay 411,

after each digit, restores the counting relays to normal in the usual way.

It may be noted here that an impulse of ground is transmitted over conductor 376 at intervals of, for example, every 4% seconds.

The first impulse on this conductor after the switch G is seized operates relay 410 which looks by way of contacts 445 and 429 to groundat contacts 424. Relay 410' connects relay 409 to the conductor 37 6 at contacts 444. However, in case the calling subscriber dials a digit before the elapse of an additional interval of 4 seconds, relay 403 will open the holding circuit of relay 410 at contacts 429 and relay 410 will accordingly release. .In the event that the subscriber failsto dial within the above interval, or in case an incomplete number has been dialled and relay 403 is not again operated, the ground on conductor 376 will energize the lower winding of relay 409 which'opposes the upper winding of the relay, and relay 409 will restore and remove ground from conductor 398 at contacts 442. This operation will initiate the switch-over at the repeater as will be subsequently explained.

The connection of relay 409 to the dial leg conductor 380 of the trunk when an idle regenerating repeater is seized, and the interruption of this connection to retransmit impulses has been described.

Referring now to Fig. 7, parts 1 and 2, in which is shown the repeater terminating the distant end of the trunk line, battery on conductor 380 through retardation coil RT, trunkconductor 715, retardation coil RTl, conductor 716, contacts 762 and 727, upper winding of relay 702 to ground,causes relay 702 to operate. It may be mentioned here that the trunk line shown is composited according to the well known manner, but that a simplexed line will obviously operate equally well. Relay 702 upon operating, closes a circuit from ground, contacts 733, winding of relay 703, windings oi relay 704 to battery and in parallel with relay 704, through contacts 760 and 760, magnet 710 of the dis criminating switch DS to battery. Relay 703 operates, but due to its resistance, relay 704 and the magnet do not operate. Relay 703 closes points in the impulsing circuit at contacts 7 35 and 741, connects ground to the local holding conductor 789 at contacts 737, prepares the local impulsing circuit at contacts 739, and prepares a holding circuit for itself at contacts 738. Ground on conductor 7 89 by way or contacts 722, conductor 787, offnormal contacts 907 of selector S2, (Fig. 9) through the lower winding of relay 901 to battery, energizes relay 901. Relay 901 re moves the short circuit from its upper winding by opening contacts 915 and connects its two winding series at contacts 916 to be efiective when off-normal contacts 907 operate 011 the first vertical step.

The second digit of the called number is retransmitted by the regenerating repeater G, as previously described, the circuit of relay 702 being opened five times in this case. Relay 7 2 accordingly responds, dropping back live times to short-circuit relay 703 by closing contacts 734, thereby operating relay 7 04 and magnet 710 of discriminating switch DS. telay 704 is slow-acting due to its series connection with relay 703 and remains operated throughout the series of impulses. Magnet 710 responds in the usual way and advances wiper 713 to the fifth contact of the bank. Relay 702 further transmits five impulses to the impulse relay of selector S2 over a circuit extending from ground, contacts 732, 735, and 718, upper righthand winding of repeating coil RG1, contacts 717, conductor 7 88, rotary oil-normal contacts 906 of selector S2, through the windings of relay 902 to battery. Relay 704 meanwhile has disconnected relay 705 from conductor 786 for purposes to be described hereinafter. Relay 704 also connects battery to the lower talking conductor of the trunk through resistance 712, contacts 744, 741, and 729, lower right-hand winding of repeating coil RC1, contacts 730, conductor 788. The battery 011 the lower talking conductor has no utility in the present instance. Relay 902 of selector S2 responds to the impulse energizing five times to close a circuit from ground, contacts 917, normally closed rotary off-normal contacts 909 and 910, contacts 920, lower winding of relay 903 to battery and in parallel therewith, contacts 921, winding of vertical magnet 905 to battery. Relay 903 energizes and opens the circuit of the rotary magnet at contacts 925. The vertical magnet also responds and raises the switch wipers opposite the called level in this case level five.

Shortly after the last impulse of the series, relay 704 restores and reconnects relay 705 to the upper talking conductor of the trunk which is without efl ect, however, at this time.

In the selector relay 903 restores shortly after the last impulse of the series, it being rendered slow-to-release by the short circuit of its upper winding closed at contacts 923. Relay 903 on restoring closes a circuit from ground, contacts 919 of relay 902 which restored after the last impulse, contacts 925, off-normal contacts 908 which close on the first vertical step of the wipers, winding of rotary magnet 904 to battery. magnet operates over this circuit and steps the wipers 927 929 in on the first set of contacts in the fifth level. lVith the first rotary step of the wipers, rotary oil-normal contacts 900, 909, and 910 open. The selector now hunts for an idle trunk, that is, one marked by battery on the test conductor. Assume that the trunk comprising conductors 933- 935 is the first idle trunk. When the wipers come to the contacts associated with this trunk, battery through the relay of switch S3 (corresponding to relay 901 of switch S2) over conductor 934, wiper 928, the two upper windings of relay 903 in series, contacts 912 to ground, will cause relay 903 to operate and open the rotary stepping circuit at contacts 925. The talking conductors will be connected through at contacts 922 and 926 and the high resistance middle winding of relay 903 will be short circuited at contacts 923 to mark the trunk busy to other selectors in the exchange.

Referring now to repeater R1, Fig. 7, when relay 704 deenergizes, shortly after the last impulse of the series, a circuit is closed from ground, contacts 737, 743, and 784, wiper 713 which is now standing on the fifth contact of its bank, through the multipled contacts and winding of relay 707 to battery. Relay 707 operates and locks to ground on the local holding conductor 789 at contacts 764, opens apoint in the circuit of relay 701 at contacts 763, disconnects stepping magnet 710 from in series with relay 703 at contacts 766, and short circuits the high resistance lower winding of relay 704 at contacts 765. The purpose of short circuiting the lower winding of relay 704 is to increase the current flow in the circuit in order that relay 703 will not deenergize when magnet 710 is disconnected.

The third digit of the called number, that is, the second to be transmitted over the trunk line, or the digit 4, is repeated in the same way by relay 702 and operates the selector S3 to the fourth level. This selector then cuts in and rotates in search of an idle trunk. It will be assumed too that the trunk comprising conductors 930-938 extending to connector Cl is the one selected. The switching relay of selector S3, corresponding to the relay 903 of selector S2, and relay 1001 of the llllllllllllllllll The rotary 

